Fractional order convergence rate estimates of finite difference method on nonuniform meshes.
Galerkin proper orthogonal decomposition methods for parameter dependent elliptic systems
Proper orthogonal decomposition (POD) is a powerful technique for model reduction of linear and non-linear systems. It is based on a Galerkin type discretization with basis elements created from the system itself. In this work, error estimates for Galerkin POD methods for linear elliptic, parameter-dependent systems are proved. The resulting error bounds depend on the number of POD basis functions and on the parameter grid that is used to generate the snapshots and to compute the POD basis. The...
Goal-oriented error estimates including algebraic errors in discontinuous Galerkin discretizations of linear boundary value problems
We deal with a posteriori error control of discontinuous Galerkin approximations for linear boundary value problems. The computational error is estimated in the framework of the Dual Weighted Residual method (DWR) for goal-oriented error estimation which requires to solve an additional (adjoint) problem. We focus on the control of the algebraic errors arising from iterative solutions of algebraic systems corresponding to both the primal and adjoint problems. Moreover, we present two different reconstruction...
Gradient-free and gradient-based methods for shape optimization of water turbine blade
The purpose of our work is to develop an automatic shape optimization tool for runner wheel blades in reaction water turbines, especially in Kaplan turbines. The fluid flow is simulated using an in-house incompressible turbulent flow solver based on recently introduced isogeometric analysis (see e.g. J. A. Cotrell et al.: Isogeometric Analysis: Toward Integration of CAD and FEA, Wiley, 2009). The proposed automatic shape optimization approach is based on a so-called hybrid optimization which combines...
Guaranteed and robust a posteriori error estimates for singularly perturbed reaction–diffusion problems
We derive a posteriori error estimates for singularly perturbed reaction–diffusion problems which yield a guaranteed upper bound on the discretization error and are fully and easily computable. Moreover, they are also locally efficient and robust in the sense that they represent local lower bounds for the actual error, up to a generic constant independent in particular of the reaction coefficient. We present our results in the framework of the vertex-centered finite volume method but their nature...
Hierarchical grid coarsening for the solution of the Poisson equation in free space.
Higher Order Convergence Results for the Rayleigh-Ritz Method Applied to Eigenvalue Problems: 2. Improved Error Bounds for Eigenfunctions.
How to recover the gradient of linear elements on nonuniform triangulations
We propose and examine a simple averaging formula for the gradient of linear finite elements in whose interpolation order in the -norm is for and nonuniform triangulations. For elliptic problems in we derive an interior superconvergence for the averaged gradient over quasiuniform triangulations. A numerical example is presented.
Hyperbolic wavelet discretization of the two-electron Schrödinger equation in an explicitly correlated formulation
In the framework of an explicitly correlated formulation of the electronic Schrödinger equation known as the transcorrelated method, this work addresses some fundamental issues concerning the feasibility of eigenfunction approximation by hyperbolic wavelet bases. Focusing on the two-electron case, the integrability of mixed weak derivatives of eigenfunctions of the modified problem and the improvement compared to the standard formulation are discussed....
Hyperbolic wavelet discretization of the two-electron Schrödinger equation in an explicitly correlated formulation
In the framework of an explicitly correlated formulation of the electronic Schrödinger equation known as the transcorrelated method, this work addresses some fundamental issues concerning the feasibility of eigenfunction approximation by hyperbolic wavelet bases. Focusing on the two-electron case, the integrability of mixed weak derivatives of eigenfunctions of the modified problem and the improvement compared to the standard formulation are discussed. Elements of a discretization of the eigenvalue...
Hyperbolic wavelet discretization of the two-electron Schrödinger equation in an explicitly correlated formulation
In the framework of an explicitly correlated formulation of the electronic Schrödinger equation known as the transcorrelated method, this work addresses some fundamental issues concerning the feasibility of eigenfunction approximation by hyperbolic wavelet bases. Focusing on the two-electron case, the integrability of mixed weak derivatives of eigenfunctions of the modified problem and the improvement compared to the standard formulation are discussed. Elements of a discretization of the eigenvalue...
Hyperbolic wavelet discretization of the two-electron Schrödinger equation in an explicitly correlated formulation
In the framework of an explicitly correlated formulation of the electronic Schrödinger equation known as the transcorrelated method, this work addresses some fundamental issues concerning the feasibility of eigenfunction approximation by hyperbolic wavelet bases. Focusing on the two-electron case, the integrability of mixed weak derivatives of eigenfunctions of the modified problem and the improvement compared to the standard formulation are discussed....
Implicit a posteriori error estimation using patch recovery techniques
We develop implicit a posteriori error estimators for elliptic boundary value problems. Local problems are formulated for the error and the corresponding Neumann type boundary conditions are approximated using a new family of gradient averaging procedures. Convergence properties of the implicit error estimator are discussed independently of residual type error estimators, and this gives a freedom in the choice of boundary conditions. General assumptions are elaborated for the gradient averaging...
Improved Difference Schemes for the Dirichlet Problem of Poisson's Equation in the Neighbourhood of Corners.
Improved flux reconstructions in one dimension
We present an improvement to the direct flux reconstruction technique for equilibrated flux a posteriori error estimates for one-dimensional problems. The verification of the suggested reconstruction is provided by numerical experiments.
Improved successive constraint method based a posteriori error estimate for reduced basis approximation of 2D Maxwell's problem
In a posteriori error analysis of reduced basis approximations to affinely parametrized partial differential equations, the construction of lower bounds for the coercivity and inf-sup stability constants is essential. In [Huynh et al., C. R. Acad. Sci. Paris Ser. I Math.345 (2007) 473–478], the authors presented an efficient method, compatible with an off-line/on-line strategy, where the on-line computation is reduced to minimizing a linear functional under a few linear constraints. These constraints...
Indicateurs d’erreur en version des éléments spectraux
Inf-sup stable nonconforming finite elements of higher order on quadrilaterals and hexahedra
We present families of scalar nonconforming finite elements of arbitrary order with optimal approximation properties on quadrilaterals and hexahedra. Their vector-valued versions together with a discontinuous pressure approximation of order form inf-sup stable finite element pairs of order r for the Stokes problem. The well-known elements by Rannacher and Turek are recovered in the case r=1. A numerical comparison between conforming and nonconforming discretisations will be given. Since higher order...
Integral equations of the linear sloshing in an infinite chute and their discretization.
Interior and superconvergence estimates for mixed methods for second order elliptic problems